Printable release

ABSTRACT

The present invention is directed to a printable release composition used for pressure sensitive labels and the like. The invention is also directed to an article, such as a label, that comprises a substrate such as paper, optionally a thermal transfer primer coating coated onto the substrate and a release layer coated onto the transfer primer coating or onto the substrate. The printable release composition of the present invention may be used with labels having permanent, repositionable or removable adhesives. The particular composition of the release layer depends on the type of adhesive that is appropriate for the desired end use.

This is a division of application Ser. No. 08/189,632, filed Feb. 1,1994, which is now U.S. Pat. No. 5,478,880.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to printable release compositions forpressure sensitive adhesive articles, such as labels, and to articlescontaining such release compositions.

2. Description of the Prior Art

Many types of adhesive articles are known, such as labels, tapes, andnote pads. Labels, in particular, are used for business forms, files,advertising, and the like. Labels come in a variety of shapes and sizes,such as window labels, machine labels, integrated labels and the like.Integrated labels are physically integrated, during manufacture, withbusiness forms, mailings and the like.

The type of adhesive best suited for use with a particular articledepends on the article's ultimate use. The adhesive may berepositionable, permanent or removable. For instance, it may bedesirable for some applications to permanently affix an article to anobject, for example, a label applied to a file folder. Such applicationsrequire a permanent adhesive. A repositionable adhesive, on the otherhand, can be applied to an object, removed, and reapplied. Pads ofnotes, for example, NoteStix or PostIt notes, are examples of articlesusing repositionable adhesives. CleanTac is an example of a label havinga repositionable adhesive. Finally removable adhesives are appropriatewhen the article is to be removed after use, but is generally notreusable. Removable adhesives may, however, also include adhesives whichbecome permanent over time.

Regardless of their use, adhesive articles must be stored and readilyavailable for use. Such articles may utilize a separate disposable linerin juxtaposed face-to-face contact with the adhesive substrate with arelease material coated on the side of the liner in contact with theadhesive side of the adhesive substrate. Just prior to use, the liner ispeeled away from the adhesive. Such an adhesive article is oftenreferred to as a "linered" label. Alternatively, the adhesive articlemay be a substrate coated on one side with a release material and coatedon the opposite side with an adhesive material. Such a linerless labelcan be stored in pads or rolls.

The release coating facilitates either the removal of theadhesive-coated substrate from the liner or the pad or the unwinding thelinerless label from the roll. The release coating needs to havesufficient adhesion to keep, for example, the linered label on itsbacking, or the linerless label on a pad or in a roll, but must havesufficient release properties to allow the label to be removed from thebacking or pad or to be unwound from the roll, while maintaining itsadhesive property.

For some time there have been problems in producing a release coatingthat possesses the above properties and that, additionally, containsprinted matter. One problem relates to retaining the tenacity of theprinted matter on the substrate so that the printed matter is not pulledoff by the adhesive or wiped off by contact occasioned by someonerubbing against or applying the label. Another problem is "fill-in" ofletters such as "o", "a", "e", etc. Fill-in occurs when the porosity ofthe substrate is not sufficient to absorb the ink and the ink has atendency to feather out. Wipe-off and related problems may occur if theporosity of the substrate is too low and the ink does not drysufficiently.

As an example of the above-mentioned problems, a release coating may beused for the printing of Postnet barcodes and FIM codes for automatedmail processing. Postnet (Numerical Encoding Technique) is used toencode the ZIP code or ZIP+4 code on an envelope and is located in thelower right portion of a mail piece. FIMs (Facing Identification Marks)are used to identify Business Reply Mail and are a series of verticalbars printed in the upper middle portion of the mail piece just to theleft of the postage indicia. FIMs greatly facilitate the automatedprocessing of the mail; thus the quality and placement of the barcodesis very critical to the success of automated processing techniques. Forinstance, in a linerless label application, the barcode or barcodes areprinted on the release surface of a substrate. If feathering or wipe offof the printed indicia occurs, then the information contained in therespective barcodes cannot be scanned. This may result in the loss ofthe cheaper bulk mailing rate. Standard postage for each piece must thenbe paid, increasing the cost to the customer, and the mail must bemechanically sorted, causing delay.

In the case of thermal transfer printing, not only is a high surfaceenergy preferred, but the surface must be very smooth. Most thermalsubstrates contain clay coatings with relatively high surface energy andbending properties to enhance ink transfer and anchorage. A releasecoating imparts a lower surface energy to the face of the label forbetter release characteristics, making printing much more difficult.Thus, higher surface energy provides higher print quality, whereas lowersurface energy provides for better release characteristics. Thus, thereis a need for a printable release coating having both a good qualityprint and good release characteristics.

SUMMARY OF THE INVENTION

The present invention relates to printable release compositions for usewith pressure sensitive adhesive articles, particularly labels. Therelease compositions provide appropriate release properties for thedifferent adhesives: repositionable, permanent and removable.

The present invention is directed to a composition for uses as a releaselayer for a permanent adhesive comprising a mixture of:

(a) about 50 to about 95 parts by weight polyethylene; and

(b) about 5 to about 20 parts by weight silicon emulsion.

The present invention is also directed to a composition for use as arelease layer for a repositionable adhesive comprising a mixture of:

(a) a major amount of ethylene vinyl chloride copolymer; and

(b) a minor amount of polyethylene emulsion.

In another embodiment, the present invention is directed to acomposition for use as a release layer for a repositionable adhesivecomprising:

(a) about 10 to about 80 parts by weight of a surfactant; and

(b) about 20 to about 90 parts by weight of an acrylic polymer.

In a further embodiment, the present invention is directed to an articlecomprising a substrate, a thermal transfer primer coating on thesubstrate, and a release layer on the thermal transfer primer coatingwherein the thermal transfer primer coating comprises:

(a) about 20 to about 50 parts by weight of a latex; and

(b) about 50 to about 80 parts by weight pigment.

Additional advantages of the invention will be set forth in part in thedescription which follows, and in part will be obvious from thedescription, or may be learned by the practice of the invention. Theadvantages of the invention may be realized and obtained by means of theelements and combinations particularly pointed out in the claims.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the present invention as claimed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is directed to an ink jet, video jet, and thelike, printable release composition for use with pressure sensitiveadhesives, such as labels and the like. The invention is also directedto an article, such as a label, that comprises a substrate such aspaper, optionally a thermal transfer primer coating coated onto thesubstrate, and a release layer coated onto the thermal transfer primercoating or onto the substrate. The label may be either linerless orlinered. The printable release composition of the present invention maybe used with labels having permanent, repositionable or removableadhesives. The particular composition of the release layer depends onthe type of adhesive that is appropriate for the desired end use.

In accordance with the present invention, as embodied and broadlydescribed herein, a composition is provided for use as a release for apermanent adhesive. This composition comprises a mixture of:

(a) about 50 to about 95 parts by weight polyethylene; and

(b) about 5 to about 20 parts by weight silicon emulsion.

Preferably, the polyethylene has a melting point of 100° C. or higher.The polyethylene is preferably an emulsion and may be obtained fromcommercial sources such as MICHEM 460, from Michelman, Inc., which is apolyethylene emulsion, having a density of 8.3, a pH of 10.1, a meltingpoint of 110° C., and a hardness of 1.5. Other emulsions that can beused include Michem 32535, 74040, 46025 and 6872 5, also from Michelman,Inc. Preferably, the composition contains about 80 to about 95 parts byweight polyethylene.

The silicon emulsion preferably contains an organopolysiloxane, such asmethylhydrogen polysiloxane, for example, SYLOFF 1171 available from DowCorning Corporation, or dimethyl polysiloxane, for example, "PC-107"available from Rhone-Poulenc. Preferably, the composition contains about5 parts by weight silicon emulsion.

The composition may further comprise up to about 20 parts by weightethylene vinyl chloride copolymer. The ethylene vinyl chloride copolymerblend may be, for example, VALCOAT 531 available from Air Products &Chemicals, Inc.

The composition may also contain other additives which do not adverselyaffect the desired properties of the release, such as pigments,thickeners, binders and amphipathic materials.

Examples of pigments that can be included in the thermal transfer primercoating composition include, for example, BURGESS No. 28, available fromBurgess Pigment, and SUPERMITE, available from ECC International. Avinyl acetate ethylene binder also may be used in the thermal transferbarrier coating composition of the invention, such as AIRFLEX 1650, fromAir Products. Examples of suitable binders that can be included in thethermal transfer barrier coating composition include, for example,AIRFLEX 100 HS from Air Products Corp., CARGILL 6431 from Cargill,KRISTALEX 3070 from Hercules, REICHHOLD 68-010 from Reichhold Chemical,and UCAR LATEX 376 from Union Carbide. Amphipathic materials that can beincluded in the release composition include ALIPAL CD-128 from GAFCorp., PLURONIC L-101 from BASF Corp., surfactant M-310 from Texaco,TEXAPHOR 963 from Henkel Corp., and TRITON GR5M from Union Carbide andamphipathic surfactant AEROSOL 22, C₂₆ H₄₃ NO₁₀ Na₄ S, from AmericanCyanamid Co. The amphipathic materials increase the release and printingproperties.

In accordance with the invention, as embodied and broadly describedherein, a composition is provided for use as a release for arepositionable adhesive which comprises a mixture of:

(a) a major amount of ethylene vinyl chloride copolymer; and

(b) a minor amount of a polyethylene emulsion.

Polyethylene emulsions that can be used in the invention include, butare not limited to, MICHEM 460, MICHEM 32535 MICHEM 68725, MICHEM 74040and MICHEM 46025. Preferably, the composition contains about 60 to about90 parts by weight ethylene vinyl chloride copolymer, and mostpreferably about 75 parts by weight ethylene vinyl chloride copolymer.

Ethylene vinyl chloride copolymers blends that can be used in theinvention include, but are not limited to, VALCOAT 531. Preferably, thecomposition contains about 10 to about 40 parts by weight polyethyleneemulsion, and most preferably about 25 parts by weight polyethyleneemulsion.

The composition can also contain other additives which do not adverselyaffect the desired properties of the release, such as the pigments,thickeners, binders and amphipathic materials described above.

In accordance with the invention, as embodied and broadly describedherein, a release composition is provided which comprises:

(a) about 10 to about 80 parts by wet weight of a surfactant; and

(b) about 20 to about 90 parts by wet weight of an acrylic copolymer.

The surfactant may be selected from, for example, sulfosuccinamatecompounds, preferably tetrasodium N-(1,2-dicarboxyethyl)-N-octadecylsulfosuccinamate. Other surfactants include SURFACT M-310 (Texaco),ALIPAL CD-128 (GAF Corp) and TRITON GR5M (Union Carbide). A particularsulfosuccinamate that may be used in the invention is AEROSOL 22,available from American Cyanamid Co. The release composition preferablycontains about 20 to about 60 parts by weight of a surfactant. Thecomposition may also contain calcium stearate, in a MICHEM 170 emulsion.

The acrylic copolymer may be selected from, for example, commercialformulations such as ACRYSOL ASE-60 from Rohm and Haas Co. Anothersource is ALCOGUM L-31, from Alco Chemicals. The release compositionpreferably contains about 40 to about 80 parts by weight of an acryliccopolymer.

The release composition described above comprising a surfactant and anacrylic polymer is particularly suited for use as an ink-jet printablerelease. The release composition works well with the ink-jet to acceptink due to proper porosity and release. The ink is partially absorbedinto the substrate so that it dries quickly and does not feather. Waterbased ink-jet, such as VideoJet, produces better print quality anddrying times with formulas consisting of at least 50 parts of acrylicpolymer. Better print quality and drying time for oil based ink-jet,such as Trident, require at least 60 parts of the acrylic polymer.

The release suited for use as an ink-jet printable release may alsocontain about 10 to about 20 parts by weight calcium stearate emulsionsuch as MICHEM 170 by Michelman, Inc. for enhanced edge definition.

The ink-jet printable release may be coated on substrates, preferably20# or 24# standard paper, such as 24# Union Camp Alkaline. The ink-jetrelease compositions are preferably coated at 0.37-1.8 gsm using a meyerrod, dahlgren, reverse roll, direct gravure, reverse gravure, direct andoffset flexo. The release layer is printable with flexo, litho, gravureand dot matrix and laser.

Any of the release compositions described above may be coated on asubstrate such as paper to obtain an article, preferably a label. Thearticle may be prepared by coating the release composition onto at leasta portion of one side of the substrate. A layer of a thermal transferprimer coating may be juxtaposed between the substrate and the releaselayer.

The article may contain a permanent or repositionable adhesive dependingon its intended use. The release layer composition should be selectedaccordingly. The adhesive is applied either on the side of the substrateopposite the release layer, e.g., a linerless label, or on at least aportion of one side of a different substrate, wherein the adhesive layeris in juxtaposed contact with the release layer, e.g., a linered label.

Improved image quality may be obtained on plain paper (e.g., Finch Fine24# stock) if the paper has been pre-coated with a thermal transferprimer coating. A thermal transfer primer coating provides for asmoother contact surface between the paper and the printhead. It alsoacts as an insulating layer or barrier by keeping the heat generatedduring the printing operation from penetrating into the paper. Printingribbons have a wax coating which melts to release the ink. By keepingthe heat on the surface, the ink is forced to print on the releasesurface, improving the print quality and producing a superior image. Thethermal transfer primer coating also functions to bind the releasecoating to the substrate, enhancing the scratch and scuff resistance ofthe release.

Instead of a thermal transfer primer coating, a barrier coating may beprovided between the substrate and the release, which may be, forexample, vinyl acetate/ethylene copolymers such as AIRFLEX 1650 by AirProducts.

In accordance with the invention, as embodied and broadly describedherein, an article is provided comprising a substrate, a thermaltransfer primer coating coated on the substrate, and a release layercoated on the thermal transfer primer coating. The thermal transferprimer coating comprises:

(a) about 20 to about 50 parts by weight of a latex; and

(b) about 50 to about 80 parts by weight pigment.

The pigment may be selected from, for example, ROPAQUE 84, by Rohm andHaas Co. The pigment preferably has a small particle size to obtain asmooth coating. Preferably, the thermal transfer primer coating includesabout 80 parts by weight of pigment.

The latex may be, for example, commercial formulations such as LATEX 620by Dow Chemical. Preferably, the thermal transfer primer coatingincludes about 20 parts by weight of a latex.

The substrate usable in the invention are preferably #24 or #20 paper.Commercial paper may be used such as 20# Finch Fine, Consolidated, andother types of thermal transfer sheets commercially available. Othersubstrates include films, TYVEK, polyester, and the like. The coatingweight of the thermal transfer primer coating is preferably 2.5 to 4.0gsm, and more preferably 2.8 gsm to 3.8 gsm. The coating weight of therelease composition is preferably 5.0 gsm to 8.0 gsm, and morepreferably 5.6 gsm to 7.5 gsm.

The substrate is precoated with the thermal transfer primer coating, ifdesired, then a release composition is prepared and coated on thethermal transfer primer coating, or on the substrate if no thermaltransfer primer coating is present, using a coater, such as a Meyer Rodcoater. Alternate methods are dahlgren, flexo, gravure blade or roll toroll. Preferably, a No. 28 Meyer Rod is used. A Meyer Rod is a coatingrod or bar having different size diameters that can be selected forapplying different amounts of coating.

The release composition described above comprising a surfactant and anacrylic polymer is particularly suited for use as an ink-jet printablerelease.

Water based ink-jet, such as VideoJet, produces better print quality anddry times with formulas consisting of at least 50 parts of acrylicpolymer. Better print quality and dry time for oil based ink-jet, suchas Trident, require at least 60 parts of the acrylic polymer.

The ink-jet printable release may also contain 10 to 20 parts calciumstearate emulsion such as MICHEM 170 by Michelman, Inc. for enhancededge definition.

The ink-jet printable release is coated on substrates, preferably 20# or24# standard paper, such as 24# Union Camp Alkaline.

The ink-jet release compositions are preferably coated at 0.37-1.8 gsmusing a meyer rod, dahlgren, reverse roll, direct gravure, reversegravure, direct and offset flexo. The release layer is printable withflexo, litho, gravure and dot matrix.

The following examples are illustrative, and are not intended to limitthe scope of the present invention.

Examples 1 and 2 are directed to release compositions for use withrepositionable adhesives.

EXAMPLE 1

A substrate was prepared by precoating with a thermal transfer primercoating.

Substrate: 24# Finch Fine Paper

Thermal transfer primer coating:

80 parts ROPAQUE 84

20 parts LATEX 620

Coat weight of 2.82 gsm

A release composition was prepared and coated on the thermal transferprimer coating of the substrate using a Meyer Rod coater with a No. 28meyer rod.

Release:

50 parts AEROSOL 22 Surfactant

50 parts ACRYSOL ASE 60

Coat weight of 5.64 gsm

Two week accelerated aging (AA) delamination values were in the 1.0-2.0oz/in range. AA was performed under heated conditions of 120° F.

EXAMPLE 2

Substrate: 24# Consolidated Thermal Transfer Paper

A release composition was prepared and coated on the substrate.

Release:

30 parts AEROSOL 22

70 parts ACRYSOL ASE-60

Coat weight 6.76 gsm

Two week AA delamination values were in the 1.0-2.0 oz/in range.

In examples 3-5, trials were conducted using the Meyer Rod coater toproduce a permanent printable release for use with a permanent adhesive.

EXAMPLE 3

A substrate was prepared by precoating with a thermal transfer primercoating.

Substrate: 24# Finch Fine paper

Thermal transfer primer coating:

80 parts ROPAQUE 84

20 parts LATEX 620

coat weight 3.76 gsm

A release composition was prepared and coated on the thermal transferprimer coating.

Release:

75 parts--Polyethylene, MICHEM 460

15 parts--Ethylene Vinyl Chloride, VALCOAT 531

10 parts--Silicone Emulsion, PCL 107

coat weight 7.5 gsm

EXAMPLE 4

A substrate was prepared by precoating with a thermal transfer primercoating.

Substrate: 24# Finch Fine paper

Thermal transfer primer coating:

80 parts ROPAQUE 84

20 parts LATEX 620

coat weight 2.82-3.76 gsm

A release composition was prepared and coated on the thermal transferprimer coating.

Release:

80 parts Polyethylene, (MICHEM 460)

10 parts VALCOAT 531

10 parts PCL 107

coat weight 5.65-7.5 gsm

EXAMPLE 5

A substrate was prepared by precoating with a barrier coating.

Substrate: 24# Finch Fine paper

Barrier:

Vinyl Acetate/Ethylene Copolymer, AIRFLEX 1650

coat weight 2.8-6.5 gsm

A release composition was prepared and coated on the barrier coating.

Release:

90 parts Polyethylene MICHEM 460

10 parts SYLOFF 1171

coat weight 5.6-7.5 gsm

None of the materials alone meets all the requirements for a goodprintable release. However, proper blends offer acceptable print andrelease.

In examples 6-8, trials were conducted using dahlgren to produce anink-jet printable release. After a 2 week accelerated aging test at 120°F., delamination values of less than 2.7 oz/in were obtained.

EXAMPLE 6

A substrate was coated with a release composition.

Substrate: 24# Union Camp Alkaline

Release:

50 parts AEROSOL 22

50 parts ASE-60

coat weight 1.5 gsm

EXAMPLE 7

A substrate was coated with a release composition.

Substrate: 24# Union Camp Alkaline

Release:

20 parts AEROSOL 22

80 parts ASE-60

coat weight 1.3 gsm

EXAMPLE 8

A substrate was coated with a release composition.

Substrate 24# Union Camp Alkaline

Release:

18 parts AEROSOL 22

72 parts ASE-60

10 parts MICHEM 170

coat weight 1.3 gsm

Examples 6-8 exhibited good drying time, good dot uniformity andcontrast and a good print contrast ratio greater than 75.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the compositions and methodsof the present invention without departing from the spirit or scope ofthe invention. Thus, it is intended that the present invention cover themodifications and variations of this invention provided they come withinthe scope of the appended claims and their equivalents.

What is claimed is:
 1. An article comprising a substrate and a releaselayer coated onto at least a portion of one side of the substrate, saidrelease layer comprising a mixture of:(a) a major amount of ethylenevinyl chloride copolymer; and (b) a minor amount of a polyethyleneemulsion.
 2. The article of claim 1, wherein the substrate is paper. 3.The article of claim 2, further comprising a permanent adhesive locatedon the side of the substrate opposite the release layer.
 4. The articleof claim 3, wherein the article is a linerless label.
 5. The article ofclaim 2, wherein the release layer is in juxtaposed contact with arepositionable adhesive coated on at least a portion of one side of adifferent substrate.
 6. The article of claim 5, wherein the article is alinered label.